The present invention relates to a magnetic tape player comprising a novel and unique electromagnetic latch device which constitutes a subcombination of the tape player and which may be advantageously employed in various apparatus unrelated to magnetic tape players.
It is desirable in magnetic tape players to be able to skip an unwanted musical or other audio selection recorded on a tape cassette and automatically resume listening upon sensing of the next selection. This feature is especially desirable in tape players for automobiles since, in the interest of traffic safety, the amount of attention which the operator devotes to manipulation of the tape player should be minimized.
This feature is provided in apparatus disclosed in Japanese patent publications Nos. 51-19766 and 51-2811 in which a play button is depressed followed by a fast forward button. An electromagnetic solenoid holds the fast forward button in the depressed position until a sensor senses a blank area of tape, at which time the solenoid releases the fast forward button to resume normal playing. With both the play and fast forward buttons depressed, the tape player operates in the cue mode. Since the alternatives to such automatic control are running the tape at fast forward until a mechanical counter indicates the position of the next selection or listening to the tape in the cue mode while holding the fast forward button depressed, the automatic control function is especially desirable, especially since it allows an automobile operator to remove his hands from the tape player and use them for control of the automobile.
The system disclosed in the above patent publications does not suffer from any particular disadvantages where employed in a large tape deck for a component type high fidelity music system for a home. This is because there is a relatively large amount of space available for mounting the solenoid inside the tape deck housing and the power requirement for the solenoid is not a matter of particular concern. However, a substantial problem does arise where such a system is incorporated in a compact tape player to be mounted in an automobile, since miniaturization is of prime concern. The power requirement for the solenoid is especially problematic where the system is incorporated in a small, battery operated portable tape player since excessive power consumption will quickly drain the batteries.
More specifically, the fast forward button is provided with a relatively strong return spring, and the solenoid must hold the fast forward button latched in the depressed position against the force of the return spring. This problem is compounded since the plunger of the solenoid exerts a force on the fast forward button in linear opposition to the force of the return spring. Thus, the force exerted on the fast forward button by the solenoid must exceed the rather strong force of the return spring. To do this, the solenoid must be disproportionately large compared to the other components of the tape player and consume a large amount of electrical power.
One means for overcoming this problem is disclosed in the above mentioned Japanese patent publication No. 51-2811 which comprises a small solenoid and a complicated mechanism for assisting the solenoid. However, the size of the mechanism is larger than the reduction in size enabled by the smaller solenoid. Thus, such as arrangement provides not only an increase in overall size, of the apparatus, but also an increase in mechanical complexity and manufacturing cost.